Localization is an important and enabling technology in many fields, and in particular in the field of robotics and especially home robotics. In home robotics, the movement of a robot in relation to the domestic environment can be a particular challenge. A robot with the ability to locate itself can work much more efficiently in tasks of area coverage (where the commonly used random methods can have a practical efficiency of about 20% of maximum possible efficiency) and point to point navigation.
Currently available localization systems are either expensive (for example scanning lasers with corner reflectors, differential GPS or inertial system), do not have adequate accuracy or require cumbersome installation. Indeed, it is particularly undesirable that a robot—whose essential purpose is labour reduction—should require a lengthy and involved setup procedure to be carried out by the user.
Examples described herein can provide a low-cost localization system which preferably can be used both outdoor and indoor and require a minimum installation. In preferred examples, the accuracy of the system can be scalable (depending on the number of transmitters).
U.S. Pat. No. 7,079,923 (Robotic Vacuum Cleaner) and U.S. Pat. No. 7,196,487 (Method and System for Robot Localization and Confinement) describe low-cost virtual wall systems for defining boundaries or area sections by means of infrared beams. However these are not used to define robot exact location but rather the boundaries of the work area.
U.S. Pat. No. 7,024,278/U.S. Pat. No. 7,188,000 (Navigation Control System for a Robotic Device) describes a localization system based on a robot sending directional beams which are received by a stationary receiver. The beams are transmitted sequentially one after the other, and are being identified through their timing from the synchronization pulse or through a different pulse width each one can be transmitted. The stationary receiver estimates the angle to the robot and the distance (roughly, by the amplitude of the received signal) and transmit those back to the robot (the data can be transmitted for further robot analysis or can be interpreted by the controller of the receiver to create a navigation command to be transmitted to the robot). The patent further describes a similar method using the stationary unit as the angular transmitter and receiving and interpreting the signals at the robot.
There are several major drawbacks to such a system:                If the beam transmitter is on the robot, there is a need for a communication link between the stationary receiver and the robot, in order to either send information regarding the location to the robot or send commands to the robot as to how to behave based on its location.        The system requires a synchronization pulse to identify the transmitting beam. This may either involve an additional system (external sync, though, for example an omni-directional infrared which is hard to implement at longer ranges), or, the use of all directional transmitters together (which is not possible in a mechanically scanning beam—an implementation which can improve accuracy/cost).        The distance estimation relies on amplitude therefore is very rough and may require calibration.        
Aspects of the present invention seek to solve or at least mitigate one or more of these and/or other problems in existing localisation systems.